It is well-known to use in subterranean applications such as mining and drilling drill bits, e.g., for gas and oil drilling, having bit bodies or portions thereof which comprise an infiltrated metal matrix. Such bit bodies typically comprise one or more cutting elements, such as polycrystalline diamond cutting inserts, embedded in or otherwise carried by the infiltrated metal matrix. The bit bodies are typically formed by positioning the cutting elements within a graphite mold, filling the mold with a matrix powder mixture, and then infiltrating the matrix powder mixture with an infiltrant metal.
The following patents and published patent applications pertain to or disclose an infiltrated matrix powder useful for forming subterranean drill bit bodies: U.S. Pat. No. 6,984,454 B2 to Majagi, U.S. Pat. No. 5,589,268 to Kelley et al., U.S. Pat. No. 5,733,649 to Kelley et al., U.S. Pat. No. 5,733,664 to Kelley et al., U.S. Patent Application Publication No. 2008/0289880 A1 of Majagi et al., U.S. Patent Application Publication No. 2007/0277646 A1 of Terry et al., all of which are assigned to the assignee of the present patent application. The following patents and published applications also pertain to or disclose an infiltrant matrix powder for bit bodies: U.S. Pat. No. 7,475,743 B2 to Liang et al., U.S. Pat. No. 7,398,840 B2 to Ladi et al., U.S. Pat. No. 7,350,599 B2 to Lockwood et al., U.S. Pat. No. 7,250,069 B2 to Kembaiyan et al., U.S. Pat. No. 6,682,580 to Findeisen et al., U.S. Pat. No. 6,287,360 B1 to Kembaiyan et al., U.S. Pat. No. 5,662,183 to Fang, U.S. Patent Application Pubication No. 2008/0017421 A1 of Lockwood, U.S. Patent Application Publication No. 2007/0240910 A1 of Kembaiyan et al., and U.S. Patent Application Publication No. 2004/0245024 A1 of Kembaiyan.
A look at a few of these patents and published patent applications will help the reader to understand the state of the art. U.S. Patent Application Publication No. 2007/0240910 A1 discloses a composition for forming a matrix body which includes spherical sintered tungsten carbide and an infiltration binder including one or more metals or alloys. The composition may also include cast tungsten carbide and/or carburized tungsten carbide. The amount of sintered spherical tungsten carbide in the composition preferably is in the range of about 30 to about 90 weight percent. Spherical or crushed cast carbide, when used, may comprise 15 to 50 weight percent of the composition and the carburized tungsten carbide, when used, may comprise about 5 to 30 weight percent of the composition. The composition may also include about 1 to 12 weight percent of one or more metal powders selected from the group consisting of nickel, iron, cobalt, and other Group VIIIB metals and alloys thereof.
U.S. Pat. No. 7,475,743 B2 discloses a subterranean drill bit that includes a bit body formed from an infiltrated metal matrix powder wherein the matrix powder mixture includes stoichiometric tungsten carbide particles, cemented tungsten carbide particles, cast tungsten carbide particles, and a metal powder. The stoichiometric tungsten carbide particles may have a particle size of −325 (45 micron) +625 mesh (20 micron) and comprise up to 30 weight percent of the matrix powder. The cemented tungsten carbide particles may have a particle size of −170 (90 micron) +625 mesh (20 micron) and account for up to 40 weight percent of the matrix powder. The cast tungsten carbide may have a particle size of −60 (250 micron) +325 mesh (45 micron) and account for up to 60 weight percent of the matrix powder. The metal powder may account for between 1 and 15 weight percent of the matrix powder and may include one or more of nickel, iron, cobalt, and other Group VIIIB metals and alloys thereof.
U.S. Pat. No. 6,682,580 B2 discloses matrix powder mixtures which may be used for producing bodies or components for wear-resistant applications such as drill bits. The matrix powder mixtures contain spheroidal hard material particles having a particle size of less than 500 microns, and preferably in the range of between 20 to 250 microns. The spheroidal hard material particles comprise between about 5 and 100 weight percent of the matrix powder. The matrix powder may also include block hard materials in the size range of between 3 and 250 microns and in the form of crushed carbides or metal powder. These block hard materials function as spacers between the spherical hard material particles to aid in the infiltration of the matrix powder. The spherical hard particles may be spheroidal carbides and are preferably spheroidal cast tungsten carbide. They also may be dense sintered cemented tungsten powders with a closed porosity or pore-free sintered cemented tungsten carbide pellets. The spheroidal carbides also may be carbides of the metals in the group consisting of tungsten, chromium, molybdenum, vanadium, and titanium. The metal powder may comprise between about 1 to 12 weight percent of the matrix powder and be selected from the group consisting of cobalt, nickel, chromium, tungsten, copper, and alloys and mixtures thereof.
U.S. Pat. No. 5,733,664 also discloses matrix powder mixtures suitable to be infiltrated to form wear element bodies or components for wear-resistant applications such as drill bits. The matrix powder mixtures include crushed sintered cemented tungsten carbide particles, wherein a binder metal comprises between about 5 and 20 weight percent of the cemented tungsten carbide composition. The crushed sintered cemented tungsten carbide powder may account for 50 to 100 weight percent of the matrix powder and have a particle size of −80 (180 micron) +400 mesh (38 micron). The matrix powder mixture may also include up to 24 weight percent of cast tungsten carbide having a particle size of −270 mesh (53 micron) with superfines removed; up to 50 weight percent tungsten carbide particles having a particle size of −80 (180 micron) +325 mesh (45 micron); and between about 0.5 and 1.5 weight percent of iron having an average particle size of 3-5 microns.
Although these earlier infiltrated metal matrices have performed in a satisfactory fashion, there is still an unfilled need for subterranean drill bit bodies for particular applications which require infiltrated metal matrices having a combination of good erosion resistance, reasonable strength, and good thermal stability. The present invention addresses that unfilled need.